Introduction to radio frequency (RF) communications – Understanding Network and Security for Far-Edge Computing

Edge computing in situations where reliable, high-speed internet access is not a given due to location or the nature of the devices involved are known as far-edge use cases. Examples include a mobile data center for disaster response, remote sensors for smart agriculture, a pilot station for a military UAV, or content delivery onboard a commercial airplane in flight.

In this chapter, we’re going to cover the following main topics:

Introduction to radio frequency (RF) communications

Utilizing cellular networks

Optimizing Wi-Fi (802.11x)-based connectivity

Connecting to low-powered devices with LoRaWAN

Integrating SATCOM in remote scenarios

Introduction to radio frequency (RF) communications

Almost all far-edge networking involves wireless networking of some type, and forms of wireless networking communicate using RFs. Wi-Fi, Cellular, LoRaWAN, SATCOM – they all use radio waves in a similar way as the radio in your car does.

Frequency and wavelength

Electromagnetic radiation consists of an electrical field that varies in magnitude, and a magnetic field oriented at a right angle to its electrical field. Both of these fields travel at the speed of light. Everything from cell phones, radio stations, and Wi-Fi access points to GPS signals are electromagnetic waves.

They are called electromagnetic because they are synchronized oscillations of electric and magnetic fields. But what does that mean? Take a look at the following figure. The part labeled E (the waves going up and down) represents the electric field and the part labeled B (the waves going left and right) represents the magnetic field:

Figure 3.1 – An electromagnetic wave

The simplest way to generate an electromagnetic wave is to make a loop of wire and move a magnet back and forth within that loop. At its core, that’s what’s happening inside of a radio transmitter. It’s just doing this at a microscopic scale, and oscillating very, very fast.

Frequency

Frequency is the number of wave cycles that pass a given point within a unit of time. It is often represented by the Greek letter Nu (n). It is measured in terms of Hertz (Hz), with one hertz representing one cycle per second.

Kilohertz – KHz, 1000Hz, or one thousand times per second

Megahertz – MHz, 1,000,000Hz or one million times per second

Gigahertz – GHz, 1,000,000,000Hz or one billion times per second

Because these waves always1 travel at the speed of light (c), there is a relationship between the frequency and the wavelength of any radio signal. The higher the frequency, the shorter the wavelength.

1 The speed of light through a given medium varies according to that medium’s refractive index. The amount of impact air has is small enough to ignore, while water slows electromagnetic waves down by as much as 25%. Light passing through a diamond slows by as much as 60%.